A conventional crawler is suspended between a driving sprocket and an idler, and is given the forwarding force by the driving sprocket's rotation.
The respective teeth of the driving sprocket are inserted in sprocket pits formed continually at the center of a crawler at regular intervals. Conventionally, since the crawler is made from rubber material so that the spaces between the sprocket pits are easily broken, the crawler cannot fulfill the duty of smoothly transferring the driving power.
To avoid this problem, conventionally, steel cores have been inserted between the respective sprocket pits so that smooth driving could be achieved, and guide rollers, which has been equipped at the outer side of guide projections formed at the cores, have prevented the crawler from leaving the driving sprocket and the idler during the operation of the crawler.
However, when the conventional crawler, in which steel cores are included, is destroyed by fire for disposal, the cores do not burn up, and this causes additional rework for disposal. Further, the increased weight of the crawler due to the cores reduces the fuel efficiency, and the separation occurs more frequently than a general sprocket-driving type.
In addition, since the friction between the metallic sprocket and the steel cores accelerates the abrasion, the lifetime of the product becomes short.
Accordingly, to avoid such problems occurring when using a conventional crawler with steel cores, configurations employing a coreless crawler were developed.
Since the prior art patent does not employ steel cores at all, the disposal can become easier and the weight is reduced, thereby improving fuel-efficiency. Since the patent uses a helical gear type driving mechanism, the capability of power transmission can be improved and the frictional abrasion can be remarkably reduced, thereby lifetime of the crawler being extended.
However, even though the prior art patent has the above advantages, it cannot avoid separation of the crawler because the deflection force, which is a common phenomenon for every crawler, is still generated. Since the crawler is operated as it is being deflected, like in FIG. 5, guide rollers, disposed at the sides of guide projections 5 formed on an inward surface of the crawler body, may rid the guide projections 5, thereby accumulating excessive strains to the crawler and lifetime of the crawler being reduced.